Negative BOLD responses (NBRs) in rat Inferior Colliculus (IC) were recently observed upon monaural auditory stimulation, but their origins and importance remain poorly understood. Intercollicular communication is proposed as a prominent mechanism for auditory processing, including sound localization/lateralization & in gain control regulation. Here, we investigated intercollicular interaction via monoaural stimulation at 9.4T. Rats exhibited NBRs in the ipsilateral IC and positive BOLD responses (PBRs) in the contralteral IC. When the contralateral hemisphere was lesioned, the NBRs vanished in the ipsilateral IC. Our findings suggest that intercollicular interaction is essential for ipsilateral negative BOLD responses and for auditory processing.